Cone-shaped targets appeared in laser target interaction after a series of key steps in the pursuit of fusion. In 1963, applications of fusion were starting to be studied (Basov, N. G. et al, Laser Driven Thermonuclear Reactions, Vol. 2, pp. 1373-1379; Paris et al., Phys. Fluids 7, 981-987; Hora et al. (1970). Conference Digest, 6th Quantum Electronics Conference, Kyoto, pp. 10-11B). Each article herein is expressly incorporated by reference in its entirety. In 1972, the laser implosion concept to produce fusion was conceived, and inertial confinement fusion research was born (John Nuckols et al., Nature, 239, 139, 1972). Some decades later, the concept of fast ignition was introduced as well as the idea of a cone target for fast ignition to allow the laser beam to get far enough into the compressed plasma to produce a fast electron beam that would deliver the ignition spark at the right place (M. Tabak et al., Phys. Plasmal, 1626 (1994); R. Kodama et al., Nature 412, 798-802 (2001)). These concepts have since been expanded. While cone geometries show an increased efficiency (Z. L Chen et al., Phys Rev E 71, 036403 (2005), and shaped flat targets have the ability to shape proton beams (S. C. Wilks et al., Phys Plasma 8, 542 (2001), higher proton beam maximum energies and lower beam divergences are still desired for a variety of laser applications.
It would thus be desirable to provide a target of specified dimensions that can produce a proton beam of a higher maximum energy and a lower divergence than current targets and that can produce proton beams that are not limited by the characteristics of the laser.